Water-soluble Pt(Ⅳ) complex with hydroxycarboxylic acid as axial ligand, preparation method and use

Abstract

The present invention discloses a water-soluble Pt(IV) complex with a hydroxycarboxylic acid as an axial ligand, a preparation method and uses thereof, and the molecular formula is trans-[Pt(NH3)4(OH)(OOCR)](NO3)2( ‑ wherein OOCR is a lactate ion, a hydrogen tartrate ion or a dihydrogen citrate ion), that is, ammonia, a hydroxyl group and a hydroxycarboxylic acid are used as inner-sphere ligands to form a six-coordinate, octahedral coordination cation with Pt(IV), and two nitrate ions are used as outer-sphere anions to play a charge-balancing role. The synthesis uses [Pt(NH3)4](NO3)2 as a starting material, first undergoes an axial oxidation reaction with an excessive amount of hydrogen peroxide to be converted into trans-[Pt(NH3)4(OH)2](NO3)2 with low water solubility, and then undergoes an axial neutralization reaction with an equimolar amount of a hydroxycarboxylic acid to obtain the target water-soluble Pt(IV) complex. The synthesis method of the present invention is simple, easy to control, and has a high yield, and is suitable for batch synthesis. This Pt(IV) complex does not contain elements harmful to the catalyst such as chlorine, sulfur, phosphine, sodium, potassium, etc., has high water solubility, and can be used for the production of industrial supported platinum catalysts.

Description

Technical Field

[0001] The present invention relates to a water-soluble Pt(IV) complex trans-[Pt(NH 3 ) 4 (OH)(OOCR)](NO 3 ) 2 ( - wherein OOCR is lactate, hydrogen tartrate or dihydrogen citrate), a preparation method thereof and its use as a catalytic precursor, belonging to the field of chemical engineering. Background Art

[0002] Supported platinum catalysts are a very important class of heterogeneous reaction catalysts, which have excellent catalytic activity, strong selectivity, high stability and long catalytic life. They are excellent catalysts for hydrogenation and dehydrogenation reactions, petroleum reforming reactions, oxidation reactions, cracking reactions, isomerization reactions, disproportionation reactions, decarboxylation reactions and deamination reactions, and are widely used in the fields of inorganic chemical industry, organic chemical industry, fine chemical industry, petroleum chemical industry, environmental protection and environmental governance, fuel cells, etc. At present, the mainstream technology for preparing supported platinum catalysts is the chemical impregnation method, and one of the key steps is liquid-phase loading, that is, loading the active components of the catalyst onto carrier materials (γ-Al 2 O 3 , SiO 2 , TiO 2 , activated carbon, etc.). As the main source of the active components of supported platinum catalysts, the composition, structure and physicochemical properties of catalytic precursors have an important impact on the performance of the prepared catalysts, and the requirements for the composition and structure of precursors are also different for catalysts with different uses.

[0003] At present, the platinum precursors used industrially are mainly chloroplatinic acid H 2 PtCl 6 and platinum nitrate Pt(NO 3 ) 2Solution (containing 10% nitric acid). However, there are obvious defects in the application of both of these catalytic precursors. For example, when using chloroplatinic acid as a precursor to prepare VOCs purification catalysts and automotive exhaust purification catalysts, the chloride ions remaining in the catalyst will significantly reduce the activity and lifespan of the catalyst; when using platinum nitrate as a precursor, since this compound is very unstable and only exists in nitric acid with a concentration greater than 10%, the resulting impregnating solution has a very strong acidity, which will corrode the surface structure of the carrier, thus affecting the performance of the catalyst. Moreover, the presence of excessive nitric acid will also release a large amount of nitrogen oxide gases during the calcination process of catalyst preparation, which is not conducive to clean production. At the same time, research and application practices in academia and industry have proved that sulfur and phosphorus are elements that are toxic to metal catalysts and will reduce catalytic activity; potassium and sodium ions will migrate within the carrier, causing the active metal to agglomerate during calcination, thereby reducing the dispersion degree and particle size of the active centers. Therefore, it is required that the catalytic precursor compound does not contain harmful elements such as sulfur, phosphorus, potassium, and sodium.

[0004] Based on the above requirements, it is of great significance to develop a platinum catalytic precursor compound with high water solubility and no harmful elements such as chlorine, sulfur, phosphorus, sodium, and potassium.

[0005] CN113278034A discloses a class of novel water-soluble Pt(IV) precursor compounds trans-[Pt(NH 3 ) 4 (OH) 2 (CH 3 COO) 2 and [Pt(NH 3 ) 5 (OH)](CH 3 COO) 3 . Although this class of precursor compounds does not contain harmful elements such as chlorine, sulfur, phosphine, sodium, and potassium, the synthesis steps of this class of catalytic precursor compounds are cumbersome and it is difficult to perform batch synthesis. SUMMARY OF THE INVENTION

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, simplify the synthesis steps, and provide a water-soluble Pt(IV) complex and its preparation method for replacing the supported platinum catalyst currently prepared using platinum nitrate (in a 10% nitric acid solution) as a catalytic precursor in industry.

[0007] To this end, the present invention provides a water-soluble Pt(IV) complex trans-[Pt(NH 3 ) 4 (OH)(OOCR)](NO 3 ) 2 ( -OOCR is lactate, hydrogen tartrate or dihydrogen citrate), with ammonia, hydroxyl and hydroxycarboxylic acid as inner-sphere ligands, forming a six-coordinate, octahedral coordination cation with Pt(IV). At the same time, the introduction of axial hydroxycarboxylic acid ligands also endows the whole complex with high water solubility. Using nitrate as the outer-sphere anion to play a charge-balancing role. Such complex molecules usually contain 0-2 water of crystallization according to different synthesis conditions.

[0008] The water-soluble Pt(IV) complex with hydroxycarboxylic acid as the axial ligand trans-[Pt(NH 3 ) 4 (OH)OOCR)](NO 3 ) 2 has the chemical structural formula as follows:

[0009]

[0010] The water-soluble Pt(IV) complex of the present invention trans-[Pt(NH 3 ) 4 (OH)(OOCR)](NO 3 ) 2 The preparation method includes:

[0011] Using the commercially available Pt(II) complex [Pt(NH 3 ) 4 (NO 3 ) 2 as the starting material, adding an excess of 30 wt.% hydrogen peroxide for axial oxidation to convert it into the poorly water-soluble trans-[Pt(NH 3 ) 4 (OH) 2 (NO 3 ) 2 , and then interacting with an equimolar amount of hydroxycarboxylic acid (lactic acid, tartaric acid, citric acid) to undergo an axial neutralization reaction to obtain the water-soluble target complex trans-[Pt(NH 3 ) 4 (OH)(OOCR)](NO 3 ) 2 . The reaction route involved is as follows:

[0012]

[0013] In addition, in trans-[Pt(NH 3 ) 4 (OH) 2 (NO 3 ) 2In an aqueous solution system reacting with hydroxycarboxylic acid, no matter how the reaction conditions are intensified (such as increasing the dosage of hydroxycarboxylic acid, raising the reaction temperature, etc.), only one of the hydroxy ligands can be substituted by the hydroxycarboxylic acid, and trans-[Pt(NH 3 ) 4 (OOCR) 2 (NO 3 ) 2 , with the structural formula:

[0014]

[0015] Compared with the prior art, the Pt(IV) complex of the present invention has the following characteristics:

[0016] (1) It does not contain elements harmful to the catalyst, such as chlorine, sulfur, phosphorus, sodium, potassium, etc., and will not have an adverse effect on the catalytic performance of the catalyst.

[0017] (2) It has high water solubility, with a solubility in water at room temperature as high as over 100 g / L, and is very stable in water, and will not decompose to produce insoluble substances even when heated to boiling.

[0018] (3) It belongs to an ionic compound. It undergoes a dissociation reaction in an aqueous solution, releasing a stable ligand cation trans-[Pt(NH 3 ) 4 (OOCR) 2 2+ , which can be effectively physically adsorbed on the surface of a negatively charged carrier, such as γ-Al 2 O 3 , modified activated carbon, etc. At the same time, the hydroxyl and carboxyl groups carried by the axial hydroxycarboxylic acid ligand can form chemical bonds with the carboxyl or hydroxyl groups on the surface of the carrier, realizing the directional anchoring of the precursor on the surface of the carrier, which is beneficial to the loading process of catalyst preparation.

[0019] (4) The synthesis process route is short, the yield is high, and the cost is relatively low.

[0020] (5) Using trans-[Pt(NH 3 ) 4 (OH)(OOCR)](NO 3 ) 2 to replace platinum nitrate (in a 10% nitric acid solution) currently used in industry as a catalytic precursor, and using the chemical impregnation method to prepare a platinum catalyst for VOCs purification, and testing its catalytic conversion performance for the common representative organic volatile gas diethyl carbonate (DEC). The results show that: the catalyst Pt / Al 2 O 3 ​The light-off temperature and conversion rate of DEC are superior to those of similar catalysts prepared using platinum nitrate as the catalytic precursor. Description of the Drawings

[0021] Figure 1 It is a graph showing the light-off characteristics of the catalytic oxidation of DEC by three Pt(IV) complexes prepared in the examples of the present invention and a catalyst prepared using commercially available platinum nitrate as the precursor. Detailed Description of the Invention

[0022] Example 1, Preparation of Intermediate trans-[Pt(NH 3 ) 4 (OH) 2 (NO 3 ) 2

[0023] Dissolve [Pt(NH 3 ) 4 (NO 3 ) 2 (100.00 g, 258.40 mmol) in 300 mL of water. Under the conditions of heating and stirring at 60 °C, gradually add 30 wt.% hydrogen peroxide (340 mL) dropwise. A large amount of white solid precipitates during the dropping process. After the dropping is complete, continue heating and stirring for 4 hours, cool to room temperature overnight, filter, wash 3 times with ice water and 1 time with ice-cold absolute ethanol in sequence, and dry to obtain 100.50 g of trans-[Pt(NH 3 ) 4 (OH) 2 (NO 3 ) 2 , with a yield of 92.39%.

[0024] Structure Characteristic Parameters:

[0025] <1>Elemental Analysis: Measured values Pt 45.88%, H 4.29%, N 19.18% (Calculated values Pt 46.31%, H 3.33%, N 19.95%).

[0026] Example 2, Synthesis of trans-[Pt(NH 3 ) 4 (OH)(OOCCH(OH)CH 3 )](NO 3 ) 2 ·2H 2 O

[0027] Add lactic acid (1.89 g, 21.00 mmol) to trans-[Pt(NH 3 ) 4 (OH) 2(NO 3 ) 2 (8.03 g, 19.07 mmol) in an aqueous solution (65 mL), stirred and reacted at 70 - 150 °C for 24 hours. After that, the solid completely dissolved to obtain a light yellow clear solution. The solution was rotary evaporated under reduced pressure until nearly dry to obtain a white solid residue, which was collected by filtration and washed 3 times with ice-cold absolute ethanol, then dried to obtain 9.31 g of trans-[Pt(NH 3 ) 4 (OH)(OOCCH(OH)CH 3 )](NO 3 ) 2 ·2H 2 O, with a yield of 92.26%.

[0028] Structural characteristic parameters:

[0029] <1>Elemental analysis: Measured values: Pt 36.69%, C 6.05%, H 4.99%, N 15.24% (Calculated values: Pt 36.86%, C 6.81%, H 4.16%, N 15.88%);

[0030] <2> 1 H NMR (500 MHz, DMSO-d 6 ) δ 6.18 - 5.40 (m, 12H, 4NH 3 ), 4.78 (d, J = 5.2 Hz, 1H, OH-lactate), 4.50 (d, J = 5.0 Hz, 1H, CH-lactate), 4.15 - 3.99 (m, 1H, OH-Pt), 3.35 (s, H 2 O), 2.50 (p, J = 1.8 Hz, DMSO), 1.22 (t, J = 7.2 Hz, 3H, CH 3 -lactate);

[0031] <3> 13 C NMR (126 MHz, DMSO-d 6 ) δ 181.32, 66.77, 39.52 (dp, J = 42.0, 21.0 Hz, DMSO), 21.07;

[0032] <4>3400 (m), 3203 (m), 1650 (s), 1383 (s), 590 (w), 535 (w);

[0033] <5>FAB + -MS: 368 [M - 2H 2 O - 2NO 3 -H] +,261[M-2H 2 O-2NO 3 -NH 3 -lactate-2H] + ,185[M-2H 2 O-2NO 3 ] 2+ .

[0034] Example 3, trans-[Pt(NH 3 ) 4 (OH)(OOCCH(OH)CH(OH)COOH)](NO 3 ) 2 Synthesis

[0035] Tartaric acid (2.77 g, 18.59 mmol) was dissolved in 25 mL of water and trans-[Pt(NH 3 ) 4 (OH) 2 ](NO 3 ) 2 (7.07 g, 16.79 mmol) in an aqueous solution (40 mL) and stirred at 70-150 ° C for 24 hours, the solid was completely dissolved to obtain a yellow clear solution, and the solution was evaporated to near dryness under reduced pressure to obtain a yellow oily residue. A large amount of ice-cold anhydrous ethanol was added to precipitate a light yellow solid, which was collected by filtration, washed with ice-cold anhydrous ethanol three times, and dried to obtain 8.50 g trans-[Pt(NH 3 ) 4 (OH)(OOCCH(OH)CH(OH)COOH)](NO 3 ) 2 , with a yield of 91.53%.

[0036] Structural characteristic parameters:

[0037] <1> Elemental analysis: measured values ​​Pt 35.65%, C 8.07%, H 3.98%, N 14.76% (calculated values ​​Pt 35.26%, C 8.68%, H 3.25%, N 15.19%);

[0038] <2> 1 H NMR (500 MHz, DMSO-d 6 )δ6.50-5.41(m,12H,4NH 3 ),4.40(d,J=14.7Hz,1H,CH-tartrate),4.27(s,1H,CH-tartrate),4.09(s,OH-Pt,OH-tartrate,H 2O), 2.50 (s, DMSO);

[0039] <3> 13 C NMR (126 MHz, DMSO-d 6 ) δ 178.18, 173.48, 73.08, 72.24, 39.52 (dp, J = 42.0, 21.1 Hz, DMSO);

[0040] <4> 3375 (m), 3241 (m), 1678 (s), 1384 (s), 590 (w), 511 (w);

[0041] <5> FAB + -MS: 261 [M - 2NO 3 -NH 3 -tartrate - 2H] + 。

[0042] Example 4, trans - [Pt(NH 3 ) 4 (OH)(OOCC(OH)(CH 2 COOH) 2 )](NO 3 ) 2 ·2H 2 O Synthesis

[0043] Dissolve citric acid (3.57 g, 18.59 mmol) in 50 mL of water, and add it to an aqueous solution (50 mL) of trans - [Pt(NH 3 ) 4 (OH) 2 (NO 3 ) 2 (7.11 g, 16.89 mmol). After stirring and reacting at 70 - 150 °C for 24 hours, a pale yellow clear solution is obtained. The solution is rotary evaporated under reduced pressure until nearly dry, and a pale yellow oily residue is obtained. Add a large amount of ice - cold absolute ethanol, and white solid precipitates. Filter and collect it, wash it 3 times with ice - cold absolute ethanol, and dry it to obtain 9.62 g of trans - [Pt(NH 3 ) 4 (OH)(OOCC(OH)(CH 2 COOH) 2 )](NO 3 ) 2 ·2H 2 O, with a yield of 90.27%.

[0044] Structure characteristic parameters:

[0045] <1>Elemental analysis: measured values Pt 30.74%, C 10.95%, H 4.67%, N 13.10% (calculated values Pt 30.90%, C 11.41%, H 3.80%, N 13.31%);

[0046] <2> 1 H NMR (500 MHz, DMSO-d 6 ) δ 5.66 (d, J = 36.5 Hz, 4NH 3 ), 4.08 (s, OH-Pt), 3.49 - 3.40 (m, 1H, OH-citrate), 3.35 (s, H 2 O), 2.83 - 2.52 (m, 4H, CH 2 -citrate), 2.50 (p, J = 1.8 Hz, DMSO);

[0047] <3> 13 C NMR (126 MHz, DMSO-d 6 ) δ 180.76, 176.73, 171.94, 73.39, 45.53, 43.25, 39.52 (dp, J = 41.8, 20.9 Hz, DMSO);

[0048] <4>3426 (m), 3202 (m), 1717 (s), 1384 (s), 592 (w), 548 (w);

[0049] <5>FAB + -MS: 470 [M - 2H 2 O - 2NO 3 -H] + , 453 [M - 2H 2 O - 2NO 3 -NH 3 -H] + , 436 [M - 2H 2 O - 2NO 3 -2NH 3 -H] + , 261 [M - 2H 2 O - 2NO 3 -NH 3 -citrate - 2H] + 。

[0050] Example 5. VOCs purification catalyst prepared using the Pt(IV) complex of the present invention as a precursor and performance evaluation

[0051] Aluminum oxide was selected as the carrier, and commercially available platinum nitrate (in the form of a 10% nitric acid solution), three Pt(IV) complexes of the present invention, trans-[Pt(NH 3 ) 4 (OH)(OOCCH(OH)CH 3 )](NO 3 ) 2 ·2H 2 O, trans-[Pt(NH 3 ) 4 (OH)(OOCCH(OH)CH(OH)COOH)](NO 3 ) 2 and trans-[Pt(NH 3 ) 4 (OH)(OOCC(OH)(CH 2 COOH) 2 )](NO 3 ) 2 ·2H 2 O were used as precursors. Four platinum-containing catalysts, numbered Pt-N (control catalyst), Pt(IV)-LN, Pt(IV)-TN, and Pt-CN, were prepared using the same impregnation method and impregnation conditions. Among them, the platinum loading was 0.3 wt.%, and the fresh sample was calcined at 550 °C for 3 h to ensure complete decomposition of the noble metal precursor.

[0052] An atmospheric pressure multi-functional micro fixed-bed reaction device was used, with an airspeed Sv of 30000 ± 500 h -1 , and the total flow rate was 6.0 L / min. The specific test conditions are listed in Table 1.

[0053] Table 1. Catalyst performance test conditions

[0054]

[0055] After mixing about 0.50 g of the catalyst sample and 4.50 g of quartz sand, they were loaded into a reaction tube with an inner diameter of 5 mm. Through a chromatograph from Fuli Company, the conversion efficiency, ignition temperature, and complete conversion temperature of the catalyst for the deep oxidation of DEC were investigated during the continuous temperature rise test.

[0056] Continuous temperature rise test: From 100 °C to 350 °C, the temperature rise time was 250 min.

[0057] The catalytic conversion performance of the four platinum catalysts for diethyl carbonate (DEC) is as Figure 1 shown, and the relevant data are listed in Table 2.

[0058] Table 2. Catalytic performance data of VOCs catalysts prepared from different precursors

[0059]

[0060] From Figure 1 and T in Table 2 50 and T 90 It can be seen that in the fresh state, the ignition characteristics of the two catalysts Pt(Ⅳ)-TN and Pt(Ⅳ)-CN prepared from the precursor of the present invention for DEC are comparable to those of Pt-N, and Pt(Ⅳ)-LN is slightly worse; however, the T 50 and T 90 of all three for DEC are better than those of Pt-N. Therefore, using the Pt(Ⅳ) complex of the present invention as a catalytic precursor can prepare a VOCs purification catalyst with excellent performance, showing good application prospects.

Claims

1. A water-soluble Pt(IV) complex with hydroxycarboxylic acid as the axial ligand, characterized in that: The molecular formula is trans-[Pt(NH 3 ) 4 (OH)(OOCR)](NO 3 ) 2 , with four ammonia, one hydroxyl group and one hydroxycarboxylic acid as the inner-sphere ligands of Pt(IV), forming a six-coordinate, octahedral coordination cation, and two nitrate anions as the outer-sphere anions; wherein -OOCR is lactate, hydrogen tartrate or dihydrogen citrate, and trans- indicates that the hydroxyl group and the hydroxycarboxylic acid ligand are in the trans position; its chemical structural formula is:

2. A preparation method of a water-soluble Pt(IV) complex with hydroxycarboxylic acid as the axial ligand according to claim 1, characterized in that including: Using the Pt(II) complex [Pt(NH 3 ) 4 (NO 3 ) 2 as the starting material, an excess of 30 wt% hydrogen peroxide is added for axial oxidation to convert it into trans-[Pt(NH 3 ) 4 (OH) 2 (NO 3 ) 2 with low water solubility, and then it interacts with an equimolar amount of hydroxycarboxylic acid to undergo an axial neutralization reaction to obtain the water-soluble target complex trans-[Pt(NH 3 ) 4 (OH)(OOCR)](NO 3 ) 2 ; the hydroxycarboxylic acid is lactic acid, tartaric acid or citric acid; its reaction route is as follows:

3. An application of a water-soluble Pt(IV) complex with hydroxycarboxylic acid as the axial ligand as described in claim 1 in preparing a supported platinum catalyst as a catalytic precursor.

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